In recent years, display components in image display devices including television receivers are being shifted from conventional cathode-ray tube display devices to thin display devices in which thin display components such as liquid crystal panels or plasma display panels are used. As a result, the image display devices are becoming thinner. Liquid crystal display devices require backlight units separately from liquid crystal panels because the liquid crystal panels do not emit light.
A technology for reducing the thickness of liquid crystal display devices disclosed in Patent Document 1 is known. A backlight unit disclosed in the document includes LEDs and a light guide plate. Each LED has a light-emitting surface through which light is emitted in a direction substantially parallel to a display surface of a liquid crystal panel. The light guide plate has a light entrance surface on a side (a side edge) so as to face the LED and a light exit surface on the top. Light from the LED enters the light guide plate through the light entrance surface and exits from the light exit surface toward the display surface of the liquid crystal display panel.    Patent Document 1: Japanese Published Patent Application No. 2001-92370